1. Technical Field
This invention generally relates to data processing, and more specifically relates to the sharing of tasks between computers on a network.
2. Background Art
Since the dawn of the computer age, computer systems have become indispensable in many fields of human endeavor including engineering design, machine and process control, and information storage and access. In the early days of computers, companies such as banks, industry, and the government would purchase a single computer which satisfied their needs, but by the early 1950""s many companies had multiple computers and the need to move data from one computer to another became apparent. At this time computer networks began being developed to allow computers to work together.
Networked computers are capable of performing tasks that no single computer could perform. In addition, networks allow low cost personal computer systems to connect to larger systems to perform tasks that such low cost systems could not perform alone. Most companies in the United States today have one or more computer networks. The topology and size of the networks may vary according to the computer systems being networked and the design of the system administrator. It is very common, in fact, for companies to have multiple computer networks. Many large companies have a sophisticated blend of local area networks (LANs) and wide area networks (WANs) that effectively connect most computers in the company to each other.
With multiple computers hooked together on a network, it soon became apparent that networked computers could be used to complete tasks by delegating different portions of the task to different computers on the network, which can then process their respective portions in parallel. In one specific configuration for shared computing on a network, the concept of a computer xe2x80x9cclusterxe2x80x9d has been used to define groups of computer systems on the network that can work in parallel on different portions of a task.
One way for computers in a cluster to cooperate to perform a task uses the concept of ordered messages. In an ordered message system, each message is communicated to all nodes, and the order of messages is enforced so that all nodes see the messages in the same order. However, there may be a need to process some special messages in an expedited manner, before messages that were previously received. For example, if one of the nodes in a cluster fails, it may be desirable to process a message indicating the failure rather than processing other messages that were received prior to the failure message. To process special messages (referred to herein as priority messages), each node must implement a common mechanism and method for processing priority messages so that the priority message may be processed out-of-order with respect to previously-received message while maintaining a common ordering of messages between nodes. Without a mechanism and method for providing and processing priority messages in a clustered computing system, the computer industry will continue to suffer from known mechanisms and methods that do not allow any message to be processed before other previously-received messages in an ordered message clustered computing environment.
According to the preferred embodiments, a clustered computer system includes multiple computer systems (or nodes) on a network that can become members of a group to work on a particular task. Each node includes a main thread and one or more work threads. The main thread receives messages from other computer systems in the group, and routes messages intended for the work thread to a response queue and a work queue in the work thread, depending on the type of the message. If the message is a response to a currently-executing task, the message is placed in the response queue in the work thread. If the message is a new non-priority task that needs to be processed, the message is routed to the work queue in the work thread. If the message is a priority message, the message is written to both the work queue and the response queue in the work thread. A priority message processing mechanism uses a priority queue defined in the work thread to assure that the priority message is processed the next time the work thread is ready to process a new task, even if the priority message was received after other tasks have been sent to the work queue.
The foregoing and other features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings.